Graphics display terminal.

摘要

The specification describes a method of storing alphanumeric characters (including special symbols) in a graphics display terminal comprising a raster-scan display device and a refresh buffer including a plurality of bit planes (1 to 6) each having a respective bit storage location corresponding to each addressible pel position on the screen of the display device. In the method, a first bit plane (luminance plane 1) stores high resolution luminance data defining alphanumeric characters each as a selection of «on» bits within a respective n x m array (character box) where n is the width of the character box in the scan line direction, and at least one further bit plane (attribute plane 2) stores low resolution colour data for the characters. The attribute plane (2) comprises a respective n-bit set of storage locations which corresponds to each n-bit wide by one pel deep portion of a character box in the luminance plane (1) and defines at least the colour and/or intensity of the foreground and background of the character for the width of the character box in respect of a single scan line. The specification also describes a graphics display terminal in which data in the luminance and attribute planes may be selectively decoded either as alphanumeric data stored as above, or as bit-mapped graphics data.